An image forming apparatus such as a digital copying machine, a laser printer, etc., forms an image by transferring a toner image onto a surface of a recording medium including printing paper, and heating and pressurizing at predetermined conditions to fix the toner image. What need to be taken into account in image forming are conditions of pressure and thermal dose at the time of fixing. In particular, in order to conduct high quality image forming, it is necessary to set fixing conditions individually according to the recording medium.
This is because image quality in the recording medium is largely affected by the quality of material, thickness, humidity, smoothness, and coating conditions thereof. For example, with respect to the smoothness, a fixing rate of toner on a concave portion in irregularities of the printing sheet surface decreases depending on the fixing conditions. Thus, uneven coloring occurs unless fixing is performed with proper conditions which are dependent on the recording medium.
Moreover, in conjunction with progress in image forming apparatuses and diversification in representation methods in recent years, there are at least several hundred types of recording media for printing paper alone. Moreover, for the respective types, there are brands which widely vary depending on differences in a specification such as a paper weight, a thickness, etc. In order to form high quality images, it is necessary to minutely set fixing conditions depending on these individual brands.
Moreover, in recent years, brands are increasing also for plain paper; coated paper such as gloss coated paper, mat coated paper, and art coated paper; a plastic sheet; and special paper, on which surface an emboss treatment is applied.
In the present-day image forming apparatus, a user himself must set the fixing conditions at the time of printing. Therefore, the user is required to have knowledge for identifying the type of paper; moreover, it is cumbersome for the user himself to input each time settings are made depending on the type of paper. Then, if there is an error with the settings, it is not possible to obtain an optimal image.
Now, Patent document 1 discloses a surfaceness discriminating device which includes a sensor which abuts against a recording material surface to scan the surface to discriminate the surfaceness of the recording material surface.
Patent document 2 discloses a printing apparatus which discriminates a paper type from a pressure value detected by a pressure sensor abutting against paper.
Patent document 3 discloses a recording material discriminating apparatus which discriminates a type of a recording material using reflected and transmitted lights.
Patent document 4 discloses a sheet material quality discriminating apparatus, wherein a material quality of a sheet material in movement is discriminated based on a reflected light amount which is reflected on a surface of the sheet material and a transmitted light amount which transmits through the sheet material.
Patent document 5 discloses an image forming apparatus which includes a determining unit which determines presence/absence of a recording material housed in a paper-supplying unit and presence/absence of the paper-supplying unit based on a detected output from a reflective-type optical sensor.
Patent document 6 discloses an image forming apparatus which irradiates light onto a recording medium to detect a light amount of two polarization components of the reflected light to discriminate the surfaceness of the recording medium.